A crop chopper typically has a chopping reel that is rotated in order to reduce crop, such as corn, alfalfa or the like, to small pieces which are then fed to a blower that propels them in a stream into a following wagon, baler, or the like. It is known to rotate the fan and chopping reel in the same direction (see German published specification No. 2,134,191). In such devices the input and output sides must be directly diametrically opposite one another so that the apparatus is relatively long. Typically, in such devices a transverse conveyor, such an an auger, is provided to transport the chopped crop from the chopping reel to the discharge blower.
It is also necessary in such devices to be able to rotate the chopping reel in reverse in order to sharpen it with a stone displaceable across the reverse rotating wheel. During the sharpening operation it is essential to decouple the fan from the drive. Thus it is necessary to provide a complicated switchover mechanism in order to allow the necessary gears or the like to be connected to the drive for the chopping reel in order to reverse same independently of the fan.